Truxene polymer and method for its preparation

ABSTRACT

THIS INVENTION RELATES TO A METHOD FOR POLYMERIZING TRUXENE WHICH COMPRISES HEATING TRUXENE IN AN OXYGEN CONTAINING ATMOSPHERE BELOW A CARBONIZING TEMPERATURE THE RESULTANT POLYMER WILL YIELD A GRAPHITE PRODUCT WHEN EXPOSED TO GRAPHITIZING CONDITIONS IF THE POLYMER IS DERIVED FROM BETA TRUXENE. IF THE POLYMER IS DERIVED FROM ALPHA TRUXENE, THE RESULTING PRODUCT IS AN AMORPHOUS CARBON. MIXTURES CONTAINING A PREDOMINANT AMOUNT OF BETA TRUXENE AND LESSER AMOUNTS OF A NON-GRAPHITIZING BINDER YIELD A GRAPHITIZED PRODUCT.

Feb. 20, 1973 w. L. HARPER ETAL 3, 7,6

TRUXENE POLYMER AND METHOD FOR ITS PREPARATION 3 Sheets-Sheet 1 OriginalFiled Sept. 9. 1968 ALPHA TRUXENE 10.15-DIHYDRO-5H-DIIN DENO [1,2 4:1,2-c] FLUORENE o o o 4 o o o 8 4 WAVE LENGTH IN MICRONS E N E R o U L F cL 2. 0h 0 F b 0 mm H OY H o o o 8 4 WAVE LENGTH IN MICRONS Feb. 20, 1973w. L. HARPER u AL. 3,717,622

TRUXENE POLYMER AND METHOD FOR ITS PREPARATION Original Filed Sept. 9,1953 3 SheetsSheet 2 I \FTOQO/Q +75/o 2.0

,I I I 1-8 '5 WEIGHT "VoflTRUXENE w 3 1.6 v A.\ o A o 5 1.4 +O,+25%'+50% TEMPERATURE,(C)

DENSITY ON GRAPHITIZATION 0F MIXTURES OF aTRUXENE 8: BTRUXENE ATDIFFERENT COMPOSITIONS AS A FUNCTION OF TEMPERATURE.

Feb. 20, 1973 Original Filed Sept DENSITY (qms/cc) W. L. HARPER ET ALTRUXENE POLYMER AND METHOD FOR ITS PRIJPARNIION 3 Sheets-Sheet. 3

ll 18 WEIGHT %,8TRUXENE TEMPERATURE (C) DENSITY 0N GRAPHITIZATION 0FMIXTURES 0F PARTIALLY POLYMERIZED FURFURYL ALCOHOL aflTRuxEN DERIVEDRESIN AS A FUNCTION OF TEMPERATURE.

United States Patent Office 3,717,622 Patented Feb. 20, 1973 3,717,622TRUXENE POLYMER AND METHOD FOR ITS PREPARATION William Lyle Harper,Wartburg, and Wesley Earl Smith, Oak Ridge, Tenn., assignors to theUnited States of America as represented by the United States AtomicEnergy Commission Original application Sept. 9, 1968, Ser. No. 758,391.Divided and this application June 10, 1970, Ser.

Int. Cl. C08f 7/02 US. Cl. 260--93.5 C 3 Claims ABSTRACT OF THEDISCLOSURE This application is a division of our copending applicationS.N. 758,391, filed Sept. 9, 1968, and now US. Pat. No. 3,535,081.

BACKGROUND OF THE INVENTION The invention described herein was made inthe course of, or under a contract with the US. Atomic EnergyCommission.

The present invention relates to the production of amorphous orgraphitic carbon from a derivative of indene.

Amorphous or graphitic carbon structures are normally made bycompounding a mixture of an organic binder with a filler material (suchas carbon, coke, decomposable organic or inorganic salts, etc.) to formeither a densified or porous product after carbonization and/orgraphitization of the binder material. Whether the final product is adensified or porous structure, the carbonized binder material will serveas the matrix and principal strength-providing source for the structure.Among the most commonly employed binders for making amorphous orgraphitic carbon structures are pitch and polymerized furfuryl alcohol.In use, a compound mixture of binder and filler is cast, molded, orpressed to the geometry and approximate dimensions of the final articleand then heat treated to a temperature in the range 900 to 1000 C. in aninert atmosphere to carboniz/e the binder. Further heat treatment at atemperature in the range 2800 to 3000 C. will, in some cases, result ina graphitized structure.

One of the principal difiiculties experienced with binders of the priorart results from the excessive loss of binder, due to volatilization,during the carbonization reaction. The extent of carbon loss is measuredby the coke yield defined as that fraction (expressed in weight percent)of an initial sample which remains as residual carbon at 1000 C. It isthus clear that a binder with a low coke yield results in considerableshrinkage in size, weight, and volume relative to its pre-cokeddimensions to yield a final structure which is relatively weak instrength.

The present invention is concerned with, and it is an object of thisinvention to provide, a novel binder in place of, or in conjunctionwith, other binders used in making amorphous or graphitic carbonarticles.

Another object of this invention is to provide an organic binder whichhas a usefully high coke yield.

A further object is to provide a method of making a graphitizable oramorphous carbon binder at will.

Still another object is to provide a method for synthesizing an organicbinder of the character described.

For the sake of clarity, the following terms are defined and will beused in the specification and claims.

(1) Coking cycle.-In general terms, a time-rate controlled curing cycledesigned to give a maximum coking yield for a particular cycle. Atypical curing cycle for truxene consists of heating in air at astepwise increase in temperature over a 48-hour period until atemperature in the range 250 to 300 C. is reached and maintained. Thisis followed by carbonization by heating for about 50 hours in an inertatmosphere to 1000 C.

(2) Graphitization.The process of heating graphitizable carbon to 2700to 3000 C. to effect orientation of its structure.

(3) Truxene.The generic name for molecules formed by the trimerizationand subsequent oxidation of indene as represented by the empiricalformula C27H13- (4) a-Truxene.-A structural isomer of truxene designatedby the formula 10,l5-dihydro-5H-diindeno-[1,2- a: l,2'-C] -fiuorene.

(5) B-Truxene.A second structural isomer of truxene designated by theformula 10,15-dihydro-5H-diindeno- [2,1-a:1',2-O]-fluorene.

(6) Graphitic carbon.A graphitic product produced by exposure of8-truxene or mixtures thereof to a car SUMMARY OF THE "INVENTION In itsproduct aspect, the present invention comprises:

(1) A thermoplastic resin resulting from the polymerization of betatruxene on heating in air to 250 C. (generally from 24 to 30 hours) to alow melting plastic res1n.

(2) The product resulting from carbonization of the thermoplastic resin;and

(3) The product resulting from graphitization of the thermoplasticresin.

In its process aspect, the present invention will deal first with aunique method for making either one of the aforementioned isomers oftruxene and then with methods for converting beta truxene to theaforementioned products (l) to (3), inclusive.

In the drawings:

FIG. 1 is an infrared spectrum of beta truxene;

FIG. 2 is an infrared spectrum of alpha truxene;

FIG. 3 is a graph on which are plotted density values of mixtures ofalpha and beta truxene which have been exposed to graphitizingtemperatures; and

FIG. 4 is a similar graph on which are plotted density values ofmixtures of beta truxene and partially polymerized furfuryl alcohol.

SYNTHESIS OF TRUXENE The starting point of our invention is based on thediscovery of a facile and unique method for making truxene. We havefound that indenes are converted to truxene when reacted in the presenceof aromatic dicarbonyl compounds (such as paraqninones orparadialdehydes) and an aliphatic tertiary amine. We have found that thenature and amount of the predominant truxene isomer will depend on thechoice of particular dicarbonyl compound used. While the role of thedicarbonyl compound in the reaction with indene is not understood, ourfindings have shown that:

(1) The dicarbonyl compound serves to initiate the reaction which leadsto a truxene product.

(2) Though not incorporated in the product, the choice of a particulardicarbonyl compound will determine which of the truxene isomers isproduced.

(3) The yield of a particular truxene isomer is proportional to theamount of dicarbonyl compound used in the reaction mixture.

(4) The tertiary amine is necessary to form truxene in the reaction ofthe dicarbonyl compound and indene.

(5) The corresponding aromatic dihydroxy compound (i.e., the reducedform) of a particular dicarbonyl com pound will react (in the absence ofa tertiary amine) with indene to produce a truxene isomer.

The following examples, I and II, are intended to illustrate typicalprocedures for forming truxene isomers.

Example I This example illustrates a typical procedure for makingfl-truxene.

To a 5-liter flask equipped with a Dean-Stark trap, reflux condenser,and stirring apparatus, were added 316 grams of 1,4-naphthoquinone(about 2 moles), 3000 grams (about 26 moles) of indene, and 30 ml. ofN,N,N',N' tetramethyl-1,3-butanediamine. This mixture was heated underreflux (-180 C.) for 30 hours, and was transferred while molten into abeaker. On cooling to 100 C., the mixture began to thicken and an equalvolume of Z-butanone was added with stirring. On cooling to roomtemperature, the mixture was filtered by vacuum filtration. The solidresidue was washed with additional Z-butanone, and then dried. A totalof 678 grams of a yellow crystalline product was collected. The productwas observed to melt at 216 to 218 C. Recrystallization from hot xyleneresulted in a melting point of 219 to 223 C. (literature 223.5 to 224.5"C.). Found: C, 94.2; H, 5.3; molecular weight, 341 (by vapor pressureosmometry), 342 (by mass spectrograph). Theoretical: C, 94.7; H, 5.3;molecular weight 342.

Our experience has shown that the water produced as a by-product of thedescribed reaction must be continuously removed during the course ofreaction in order to insure the formation of the desired truxeneproduct. While lesser amounts of water are produced if lesser quantitiesof a selected dicarbonyl compound are used, product yields will be foundto be in direct proportion to the quantity of the dicarbonyl compoundused in the reaction.

Eight fractions of the recrystallization product were collected insuccession by sublimation of a sample at 230 C. and 50 microns. Massspectrometric analysis of the purified samples indicated a mass of 342.An infrared spectrum taken of a recrystallized sample dispersed inpotassium bromide is shown in FIG. 1.

In order to confirm the identity of the product, an isomeric truxenemixture was prepared according to the procedure of Lang et al. asdescribed in Chemische Berichte 93, 321325 (1960). ,B-truxene wasisolated from the isomeric mixture resulting from the Lang et al.procedure by taking advantage of significant diiierences in thesolubility of a and B isomers in hot xylene. The isolated fl-truxene wasfurther purified by sublimation under vacuum. Its infrared spectrum wasfound to be identical to that observed for the product resulting fromthe reaction of indene and 1,4-naphthoquinone. A mixed melting point ofthe two compounds showed no depression. The nuclear magnetic resonancespectra of the two compounds were found to be identical, thus serving tofurther confirm the identity of the product.

The 1,4-naphth0quinone lost its identity during the reaction asevidenced by the loss of oxygen through the production of water and ourinability to remove unreacted 1,4-naphthoquinone from the reactionmixture. However, the presence of 1,4-dihydroxynaphthalene and1,4-naphthoquinhydrone was noted. The ease of interconversion of1,4-quinones into their corresponding hydroquinones indicates not onlythe presence of 1,4-naphthoquinone and 1,4-dihydroxynaphthalene but alsothe presence of the adduct of these compounds, 1,4-naphthoquinhydrone.The role of the aliphatic tertiary amine appears to be that of acatalyst in reducing the dicarbonyl compound to dihydroxy or quinhydroneform. This was borne out by the fact that the beta truxene was isolatedas a reaction product of 1,4-dihydroxynaphthalene and indene without thepresence of a tertiary amine.

While a specific tertiary amine was used as a base catalyst, otheraliphatic tertiary amines have been found to function effectively, amongwhich are N,N,N',N'-tetramethyl-1,4-butanediamine;N,N,N,N'-tetramethylmethylenediamine; hexamethylenetetramine;dimethylbenzylamine; tripropylamine; and N-methylmorpholine. Aromatictertiary amines have not been effective catalysts for truxene synthesis.

As previously mentioned, the apparent function of the dicarbonylcompound appears to be that it serves to selectively initiate, incombination with the tertiary aliphatic amine, the conversion of theindene to a truxene isomer. Thus, while in Example I, the reaction of1,4-naphthoquinone with indene was shown to produce beta-truxene, thereaction of indene with Z-methyl-1,4-naphthoquinone will produce atruxene rather than the fi-isomer. Table I below indicates the nature ofthe product produced from the reaction of various dicarbonyl compoundsor hydroquinones with indene.

HYDRONONES Milejlgiigg p Vapor Mass Ipifrarfii alasorpressure, specon te800- Carbonyl compound Product C.) osmometer trometer 700 em.- region2,5-dichloro-1,4-benz0quin0ne B T 2232 5 336 342 754 718lA-naphthoquinone .d 219-223 341 342 754 11a Z-methyl-l,i-naphthoquinone 3 378 I 730 2,3-dichloro-L4-naphthoqmno 730Anthraquinone a 379 730 2-methylanthraquinone a 387 7302-chlpr0authraquinone 224-228 754, 714 1,4-d1hydroxynaphthalene 5Truxene 222-224 753 712 Terephthaldehyde oz Truxene.-- a 385 7289,10-dioxo-1,4,9,1O,11,12-hexal1ydro-1,4-

methyleneanthraeene fi'lruxene 215 760 7169,10-diox0-1,4,5,8,9,l0,11,12,l3,14- a Truxene 290 730decahydro-l,4,5,8,-dimetl1yleneanthracene. 2,5-diphenyl-l,4-benzoquinoneMixture 225 383 342 730, 752, 713

ld i-dihydroxynaphthalene, a reduced form of 1 4-naphthoquinone isincluded.

H wagging region for aromatic compounds havin four adaceni; h drocarbonsin one six-membered rin 8 Melting points from difierential thermalanalysis. g 1 y g Example H This example illustrates a typical procedurefor making alpha truxene.

To a 5-liter flask equipped with a Dean-Stark trap, reflux condenser,and stirring apparatus were added 250 grams anthraquinone, 2500 gramsindene and 25 ml. of the tertiary amine,N,N,N',N'-tetramethyl-1,3-butanediamine. This mixture was heated underreflux (-180 C.) for 30 hours, and was transferred while molten into abeaker. On cooling to 100 C., the mixture began to thicken whereupon anequal volume of Z-butanone was added with stirring. On cooling to roomtemperature, the mixture was filtered by vacuum filtration. The solidresidue was washed twice with hot Xylene to remove unreactedanthraquinone, and the resulting gold product was allowed to dry. Atotal of 218.7 grams of product was collected. The melting point asdetermined by differential thermal analysis was 379 C. The literaturevalue as determined by differential thermal analysis was 375 C. Found:C, 94.6 H, 5.4; molecular weight, 342 (mass spectrograph). Theoretical:C, 94.7; H, 5.3; molecular weight, 342.

The isolated truxene product was purified by recrystallization usingxylene as solvent and then sublimed at 250 C. under vacuum. An infraredspectrum of the sublimed truxene is shown in FIG. 2.

CONVERSION OF TRUX'ENE TO POLYMER Both alpha truxene and beta truxeneare suitable carbon precursors since they have high coking yields.However, the two isomers are not equivalent for use as a binder. Thedifferences between the isomers become evident when they are eachsubjected to polymerization conditions. We have found that the fi-isomercan be converted to polymer by an oxidizing reagent such as oxygen toyield a fusible thermoplastic resin which is convertible to carbon undercoking conditions. However, the a-isomer fuses at temperatures in excessof 350 C., while fusion can be achieved at 220 C. with the 13-isomer.Moreover, the polymer resulting from polymerization of the ,B-isomer isreadily convertible to a graphite with coking yield in excess of 75%,while the a-isomer converts to amorphous (i.e., non-crystalline) carbonat equivalent coking yields.

The following example will illustrate the conversion of beta truxene toa low melting thermoplastic resin.

Example III Beta truxene samples of equal size were heated for variouslengths of time in air and in an inert (non-oxygencontaining) atmosphereat 300 C.

The samples which were heated in air were observed to lose crystallinityas signified by a decrease in melting point until a material of minimummelting point was 0)- tained. Further heating in oxygen at the same ordifferent temperatures results in an increase in fusion temperature.When heated to coking temperatures, co king yields of from 75 to 85% areobtained. 0n the other hand, sam ples that were treated at 300 C. in aninert atmosphere retained a high order of crystallinity and have muchlower coking yields (of the order of 50%) on heating the sample througha carbonization cycle. The time required to attain a given minimummelting state of the low melting beta truxene polymer has been found tobe dependent on sample size, exposed surface area, and temperature. Theeffect of the air cure treatment on the coking yield can be seen by theresults in Table 11 below.

TAB LE II [Carbonization of a-truxene and ii-truxene] 1 Air cureconsisted of heating samples in air under a controlled time rate cyclewhich reached a maximum of 300 C. after 48 hours.

The eifect of time on the fusion temperature is shown in the followingexample.

Example IV Two samples of beta truxene (preparedby the reaction ofindene with 1,4naphthoquin'one) were heated in vessels at 300 C. in airfor periods ranging from 1-31 hours. This procedure resulted in anapproximate 10 percent weight loss and produced non-crystallinepitch-like material. The change of fusion temperature with time is shownin Table III below.

TABLE III.MELTING POINT OF BETA TRUXENE ON HEATING IN AIR .A'I 300 C.

Melting point 0.)

Batch B 3 Batch A 1 Time heated at 300 0. (hrs):

1 Weight of beta truxene heated was 793 grams. F Weight of beta truxeneheated was 656 grams.

The product which melted in the range of 98 to 135 C. was a pitch-likematerial with an average molecular weight ranging from 405-460. Thesolubility of the material in xylene at room temperature was 14.2 grams/100 cc. as compared to -1 gram/ 100 cc. for beta truxene at roomtemperature. Under reflux more than 100' grams of the material dissolvedin 100 cc. of xylene as compared to a solubility of 42 grams/ 100 ml.for beta truxene at reflux.

Example V The effect of surface area on fusion point and coke yield wasmeasured by air heating beta truxene samples of the same weight invessels of various sizes, thus producing differences in amount ofexposed surface area. After heating in air the samples were thensubjected to a coking cycle. The results are summarized in Table IVbelow.

TABLE Iv THE GRAPHITIZATION EFFECT [Coke yield from 20-gra1n samples ofbeta truxene as a function of the surface area exposed during roomtemperature-to-250 0. cycle in air} P e V a We have previously comparedthe physical and chemifig: ggg gflg cal characteristics of alpha andbeta truxene and have exposed 250 0. cycle 1,000 (3. cycle shown thatthe beta isomer fuses at much lower tempera- (cmj) in'air (O(Wt-Percent) ture than the alpha isomer. A still further distinction isVessel size (1111s.): noted in the capacity of the air cured isomers toconvert 50 11.530 108-131 71.3 to fa gasgg 112%? 5611) Only the betaisomer-derived polymer yields graphitic 3:5 3 2 3: 9 carbon whencarbonized and fired to graphitizing tempera- 1 Difieren S d S n as r hd b 1 tures. While the initial air cure is essential to high coking CB 1EX 0 e u ace 8183. W 3. m is e H Samples. ofequalsizepm Vessels varyingP y Pam g yields for both lsomers, it apparently alters the fusion 1COklHg cycle included a room temperature-to-250 0. cycle in aircharacteristics of a-truxene at subcarbonization tempera- !or 48 hoursfollowed by heating in an inert atmosphere from 250 C. to

1,0000 Odor 50 houm tures suificiently to prevent graphitization athigher temfl RT=Boo1n temperature. peratures. On the other hand, aircuring of beta truxene, I i to h noted that the melting point f theathexwhile lowering the fusion temperature, does not affect the posedbeta truxene varied with surface area. More irngraphltilability ofCarbon from s SOHICe- The i m portantly, the coke yield was shown tohave increased with densities and data from X-Tay diffraclometef Scans,s increasing exposed area f beta truxene shown in Table VI below,indicate these diiferences in graphitic character.

Example VI The ,e-truxene samples after graphitizing exhibit densi- Thisexample wa undertaken to determine th fle t ties very close to thetheoretical density of graphite (2.25 of the precoking temperature inair as it relates to coking s as Well as the Characteristic gr phiteX-ray yield, fraction peak for the 002 plane. The carbon obtained fromTwenty-gram samples of beta truxene were heated in th rhad a w r ensityand no sharp air at 250 C. (Run A) and at 300 C. (Run B) for vari- X-raydiffraction peak for the 002 plane. This is characous lengths of time.These samples were then cured in air lerisiic aIIIPOYPhOI-IS Carbon- Itcan also be Seen that during a room temperature-to-250" C. cycle afterwhi h the u-isomer is relatively infusible after the 250 C. air

they were subjected to a coking cycle. Run C was heated e ment- TABLEVL-GRAPHITIZATION OF ALPHA TRUXENE AND BETA TRUXENE Angle of retlec-Coking yield l Helium tion of 002 Melting density after plane afterpoint after RT-to- RT- RT-to- RT-to-2,700 Description Sample RT-to-2501,000 O. 2,700 0. 2,700 O. 0. cycle (from of reflection size 0. cycle incycle (wt. cycle (wt. cycle (gmsJ X-ray ditfracband of 002 Sample type(gins) air 0.) percent) percent) cc.) torneter, 28 0.) plane Min.maltlng B-truxene B 20.0 B -3 71. 3 71. 3 2. 23 26. 42 Sharp.

Dofi 20. 0 128-166 76. 5 D03- 30.0 141-195 85.7 84 1 2 15 26 Do. Do. 50.0 121-138 87 4 B-Truxene- 14. 3 7 79. 1 1. 90 26. 62 Do Do. 136. 8138-172 74. 4 69. 9 2.00 26. 44 D0. a-Truxene 4 20.0 300 91. 0 83. 1 1.36 26. 30 Broad.

Do 2. 6 300 87 9 78.8 26.35 D0. D0 5 2.7 300 82 9 1 Coking cyclesinclude a room temperature-to-250 0. cycle in air as well as aroomtemperature-to-1,000 C. coking cycle. Graphitization was accomplished byfiring samples to 2,700 C.

Prepared by heating beta truxene in air at 300 C. for approximately 20hours.

3 Sample did not go through room temperature-tc-250 0. cycle in air.

4 Obtained from K and K Laboratories, Inc. Plalnview, New York.

5 Prepared from the reaction of indene and anthroquimone.

in air at 300 C. and then subjected directly to a coking In thepreceding description we have shown that beta cycle. The results aresummarized in Table V. truxene can be converted to a low meltingthermoplastic TABLE V.COKING YIELD OF BETA TRUXENE AFTER PREHEATING INAIR Melting point Melting point Coke yield Melting point Melting pointCoke yield Melting point Coke yield after preheat after RT-toalter RT-tcalter preheat after RT-toafter RT-toafter gggheit after RT-to- Length oftime preat 250 0. 250 C. cycle 1,000 6. cycle at 300 0. 250 0. eye 1,000G. cycle 1,000 0. cycle heated 3 (hrs) 0.) 0.) (wt. percent) I 0.) 0.)(wt. percent) 0.) (wt. percent) X After preheat, samples were heated ina room temperature-to-250 0. cycle in air previous to carbonizatlon in aroom temperature-t0-1,000 0. cycle as per Table IV.

2 After preheat, samples were placed directly in a room temperature-m4000 coking cycle as per Table IV. 3 All samples consisted of 20 grams ofbeta truxene which were preheated in Nil-milliliter beakers.

resin and thence to a highly graphitized product with high It will benoted that a pre-coking temperature in air 70 coking yields.

at 300 C. (Run B) resulted in higher coke yields than In the followingexamples we will show that these when a pro-coking of 250 C. (Run A) wasused. A comunique combinations of properties can be utilized withparison of Run B with with Run C indicates that the addiother bindermaterials where such other binders are othertional curing time in air at250 C. as experienced by samwise useful but for their low coking yieldor low tendency ples of Run B resulted in higher coking yields. 75 'tographitize.

9 Example VIII This example shows how one may combine a low melting betatruxene resin With a relatively low coke yield binder to yield a bindermixture which can be carbonized to relatively high coke yields. I

In this example, mixtures of air cured beta truxene and a partiallypolymerized furfuryl alcohol were air cured in a room temperature-to-250C. air cycle followed by a coking cycle. The results are summarized inTable VIII below.

TABLE VIIL-COKE YIELD OF MIXTURES F MINIMUM MELTING BETA TRUXENE ANDPARTIALLY POLYME R- IZED FURFUYL ALCOHOL 2 Used as a catalyst to effectpolymerization of furfuryl alcohol. 8 Coking cycle includes an initialroom temperature-to-250 0. cycle in air prior to a roomtemperature-to-l,000 C. coking cycle.

The clear benefit in terms of coking yields is evident from the datawhich shows a progressive increase in coking yield with increasingamounts of beta truxene.

Example 1X Varying amounts of a low melting resin derived from aircuring of beta truxene and a commercially available grade of pitch weremixed and subjected to an air cure followed by carbonization. Theresults are summarized in Table IX below.

TABLE IX.COKE YIELDS OF MIXTURES OF MINIMUM MELTING BETA TRUXENE ANDPITCH Coke yield 3 Melting point after Weight of minimum Weight of afterRT-to-1,000 C. melting B-truxene 1 pitch 3 RT-to-250 0. cycle (wt.(gms.) (gms) cycle 0.) percent) Example X In Examples VIH and IX it wasshown that the air cured resin derived from beta truxene canupgrade cokeyields of binder mixtures in which one component gives a low coke yieldwhen carbonized alone.

In this example we will show how a graphite structure can be obtainedfrom a mixture of two binders, one component of which does not normallyconvert to graphite under graphitizing conditions.

Mixtures of alpha truxene and beta truxene containing 25, 50, and 75weight percent beta truxene were air cured to 250 C., carbonized to 1000C. in an inert atmosphere and subsequently fired to 1600, 2000, 2400,and 2800 C. Helium density data on these carbons were recorded in FIG. 3as a function of temperature, along with those for alpha truxene andbeta truxene. The difference in the helium densities of carbons frommixtures containing 50 percent and 75 percent beta truxene havesignificance. Of the mixtures studied; these two compositionsrepresented a division between graphitizing and nongraphitizing carbon.Differences in the helium density data for carbons from alpha truxeneand mixtures containing 50 percent or less of beta truxene wereinsignificant. X-ray diffraction scans of these carbons after 2800 C.emphasized the differences in properties of carbons from mixturescontaining 50 and 75 percent beta truxene. Scans of the 002 planes ofthese carbons were in agreement with helium density data in that theyshowed the sharply defined peaks expected from a graphite structure.

Photomicrographs of these carbons after 2800 C. afforded anothercomparison of the mixture containing 50 and 75 percent beta truxene, andclearly illustrated a significant difference in the two carbons. Carbonfrom mixtures containing 50 percent beta truxene appeared completelyamorphous, while that from the mixture containing 75 percent betatruxene appeared highly graphitic.

The photomicrographs of the carbons from mixtures of alpha truxene andbeta truxene were compared with those obtained by initially mixing thecokes from beta truxene and alpha truxene, and firing those cokemixtures to 2800 C. In the latter case, two distinct carbon phases wereobserved regardless of the ratio in which the cokes were mixed. Thus,beta truxene and alpha truxene, acting independently produced amorphousand graphitic carbons, respectively. Helium density data on thesecarbons indicated a mere averaging of physical properties of the twocomponents. By comparison, the influence of alpha truxene on theproperties of beta truxene and vice-versa, were apparent when the twohydrocarbons were carbonized in combination. Thus, alpha truxene, thoughhighly aromatic, cannot be graphitized because it does not completelyfuse before or during carbonization. The fact that no graphitic carbonwas produced from mixtures of alpha and beta isomers containing up to 50weight percent beta truxene indicates that these mixtures have fusioncharacteristics that prohibit graphitization. The fact that mixturescontaining 75 percent beta truxene do graphitize suggests formation of asolution at elevated temperatures of alpha isomer in the excess betaisomer, thus affording suitable fusion characteristics duringcarbonization.

Example XI This example provides another illustration of how betatruxene can be used to form a graphitized carbon from a mixture ofmaterials, one of which is nongraphitizable.

Samples of partially polymerized furfuryl alcohol were air cured to 250C. carbonized to 1000 C. in an inert atmosphere, and subsequently firedto 1 600, 2000, 2400, and 2800 C. Helium density data indicated that theproduct was amorphous carbon with closed porosity at temperatures above1000 C. A photomicrograph of the carbon after 2800 C. also indicatedamorphous carbon. An X-ray diffraction scan of the 002 plane of thecarbon after 2800 C. was broad and diffuse, characteristic of anamorphous carbon.

By way of comparison, mixtures of low melting resin derived from betatruxene and partially polymerized furfuryl alcohol were air cured to 250C., carbonized to 1000 C., and subsequently fired to 1600, 2000, 2400,and 2800 C. Helium density data on these carbons are also presented inFIG. 4 (as a function of temperature), along with the data forindividual samples of unmixed beta truxene and partially polymerizedfurfuryl alcohol.

When the carbon precursor yielding a graphitic carbon was present in thegreater quantity, the graphitizability of the disordered carbon wasenhanced and the probability of closed porosity was decreased. Likewise,when present in the greater amount, the carbon precursor yielding thedisordered (i.e., amorphous) carbon appeared to inhibit graphitizationand increased the probability of closed porosity.

Mixtures containing greater than 50 percent beta truxene yielded carbonsthat increased in density at carbonizing temperatures above 1000 C.,while those with greater than 50 percent of the partially polymerizedfurfuryl alcohol underwent a decrease in density at these temperaturesand yielded a disordered carbon structure having closed porosity asdetermined by helium density measurements.

The difference in the properties of the carbons from themixtures'containing 60 to 40 percent beta truxene was significant, andrepresents a division between graphitizing and non-graphitizing carbonwith respect to this system. X-ray difiraction scans of the 002 planesof the carbons after 2800 C. and photomicrographs corroborated thehelium density findings.

Carbon from samples containing 60 percent or more of the beta truxenederived resin was graphitic with open porosity, while carbon from themixture containing 40 percent beta truxene was amorphous carbon withclosed porosity. The difiz'erence in the properties of these two carbonswas greater than would be anticipated from mere averaging of physicalproperties, as might be true for simple dilution processes.

We claim:

1. A method for polymerizing crystalline truxene which comprises heatingtruxene with an oxidizing reagent selected from the group consistingessentially of air or oxygen at a temperature in the range of 250-300 C.sulficient to erase the crystallinity of the truxene and reach athermoplastic state as evidenced by a decrease in the melting point ofthe mixture relative to the melting point of the truxene startingmaterial.

2. The method according to claim 1 wherein the truxene is beta truxene.

3. A thermoplastic resinous material comprising polymerized beta truxenederived from heating said beta truxene in an oxygen-containingatmosphere to and maintaining said beta truxene at a temperature in therange of 250- 300 C., sufiicient to convert said beta truxeneto athermoplastic resin, said resin being further characterized in that itis convertible to graphite after being coked and heated to agraphiti'zing temperature.

7 References Cited UNITED STATES PATENTS 2,157,544 5/1939 Kline 260-668F 2,21 ,001 9/1940 Dietzel 7 2 0-668 F 2,373,714 4/1945 Soday 26093.5 02,504,044 3/1970 Harper et a1 260-668 F FOREIGN PATENTS 968,215 9/19 4Great Britain 23-2094 JAMES A. SEIDLECK, Primary Examiner US. (:1. X.R.260-668 F

